This study is designed to evaluate the capability of computerized fluoroscopy to evaluate non-invasively left ventricular function, the patency of coronary artery bypass grafts, and the presence of significant obstructions in major coronary vessels. Improvement in current imaging capabilities will be accomplished by modification used. Three experimental dog studies will be performed: One is designed to relate graft flow to visualization of coronary artery bypass grafts; one will compare measures of ejection fraction and cardiac output as determined by computerized fluoroscopy to similar numbers obtained by thermodilution cardiac output and aortic flow probes; and one will attempt to relate infarct size, as determined by tetrazolium blue dye, to dyskinetic behavior as displayed by an imaging mode which produces signals proportional to the time-rate of change of left ventricular iodine content. Two human studies have been proposed. In the first, patency of bypass grafts in a group of postoperative patients will be determined by computerized fluoroscopic intravenous examination and compared to direct coronary antiography. The second human study will examine ejection fractions and compare wall motion abnormalities as determined by cardiac catheterization to similar values obtained by intravenous computerized fluoroscopy. In addition, rest and exercise ejection fractions obtained non-invasively by computerized fluoroscopy will be examined as a screening test for the presence or absence of coronary artery disease by coronary antiography.